The present invention relates to an intake port structure for an internal combustion engine having a plurality of cylinders.
Fuel distribution among cylinders of a multiple-cylinder internal combustion engine is governed by a vacuum developed in intake passages or the characteristics of an air flow by which fuel vapor is carried. To provide uniform fuel distribution among the cylinders, various means have been proposed for use in intake passages following a common intake passage of an intake manifold. The intake passages are normally arranged asymmetrically to cause an air-fuel mixture to flow in a direction tangential to the peripheral wall of each engine cylinder. Addition of the means for uniform fuel distribution to such asymmetrical intake passages results in increased resistance to the flow of the air-fuel mixture in some intake passages, with the consequence that engine performance will become poor.